It certainly seemed as though it was on because it notified me of the speed trap I marked when I left downtown. He was in the car, but why does this not matter? I know Blake said it usually shuts off after they have caught someone, but why would it detect anything at all if their radar was off? Sorry for my ignorance, it would just be nice to know so I can keep my monthly tickets to a minimum as I had planned when I bought the damn thing.

I see what happened. You marked the speed trap, and the alarm you heard from the RD was just reminding you that you marked that location, not that there was any radar being used at the moment at that location. If you marked that location, it will go off at that spot every time, regardless of whether there's a cop there or not. The cop obviously had shut off the radar, which is why you didn't get an earlier warning.